Human powered watercraft have historically been used for transport and hunting, however, modern uses more likely involve sport and recreation. The traditional design of canoes and kayaks is often repeated in modern forms of fiber glass or molded plastic. The traditional design involves a single hull which has the advantage of being quickly maneuverable. Especially in the case of sport kayaking, it is important that the kayak can be rotated about a vertical axis very rapidly to enable the paddler to maneuver around rocks and other obstacles. Traditional designs of canoes also include a single hull originally for transporting cargo, although in modern use, canoes are generally used for recreational activities. In both cases, the traditional design of kayaks and canoes is relatively unstable and the passengers must maintain balanced to avoid unintentionally tipping themselves into the water.
Another disadvantage of traditional canoe and kayak designs is the need to develop a technique for paddling in order to direct the watercraft in a relatively straight line. Novices and children often have great difficulty in propelling canoes and kayaks in a straight line and tend to zigzag across the surface of the water as they switch paddling from one side of the watercraft to the other.
While kayaks are generally smaller in size than canoes and produce as little wetted surface as possible, traditional canoe designs present a relatively large hull and develop significant water resistance or drag.
A further disadvantage of kayaks and canoes of traditional design is the inability of persons to re-enter the canoe or kayak after entering the water. In the case of the kayak, it takes great strength and practice to move from an overturned position to an upright position after the kayak tips. This is a technique practiced by expert kayakers and in general, novices and inexperienced paddlers have great difficulty in re-righting the kayak.
In the case of canoes, they generally include a buoyant float at both ends of the canoe to prevent it from sinking. Once a canoe has overturned and the passengers are floating in the water, it is very difficult to re-right the canoe and enter the canoe without tipping it over again. There are techniques for doing this especially when two persons are involved and can balance each other's weight, however, this is a very difficult maneuver beyond the ability of novices and children.
Traditional designs of kayaks and canoes remain popular because they are relatively inexpensive and simple to build and maintain. Despite the disadvantages of lateral instability and paddling difficulty, they remain popular mainly due to their simplicity of operation and well known methods of use. In contrast for example, motorized boats require fuel, generate noise and demand a higher level of care and attention to operate. Watercraft propelled by human arm or leg power are popular in that they are useable by a wide variety of people and are environmentally friendly.
Despite the above preferences for human powered watercraft, there are significant disadvantages in that kayaks and canoes of traditional design are extremely difficult to balance and quite often passengers are tipped over into the water unexpectedly. Even persons who know how to swim well are required to wear lifejackets due to the possibility of unexpected tipping and injury as the passenger collides with the boat or rocks, etc. in the water. The single hull design of kayaks and canoes enables the passenger to rotate and maneuver the personal watercraft very easily, however, this also results in a disadvantage where it requires significant skill and practice to propel a kayak or canoe in a relatively straight line. Long kayaks, due to the difficulty in turning them, often include foot pedals with cables to control a rear rudder.
The prior art is replete with various designs of human powered watercraft reflecting the popularity of this form of transport and recreation. Especially in recent times kayaking and white water rafting are becoming more popular as an adventure recreational activity and there is a desire to produce safe and practical new designs. Of particular interest are plastic or fiberglass molded bodies. These have the advantage of superior buoyancy due to an enclosed air filled cavity, ease of repair and the ability to use mass produced molding techniques common to the plastics industry.
Typical hull shapes include a generally semi-circular hull, rectangular hull and catamaran dual hull shapes. While a semi-circular hull has a comparatively moderate draft and drag, it has low stability. A rectangular shaped hull with the same bouyancy has greater stability and less draft, however, the wetted surface is higher resulting in higher drag. A dual hull catamaran concentrates the bouyancy and weight in the lateral hull areas resulting in relatively high stability with low drag due to the smaller wetted surface. The draft of a catamran hull is relatively high due to the pointed dual hulls.
A design of a molded kayak watercraft is shown in U.S. Design Pat. No. 341,351 to Arcouette. The Arcouette design includes a molded plastic body generally of the shape of traditional kayak but with an open cockpit. The Arcouette design includes a rear keel which projects into the water and impedes rapid rotation. The whole shape of the Arcouette is a traditional rounded single hull with a slightly concave mid bottom portion. This single hull, as in the case of traditional canoes, presents a relatively large wetted surface and results in increased drag and water resistance. Although the hull shape is relatively wide, the smooth rounded shape results in a boat which is easily tipped laterally as in the case of traditional kayak and canoe designs.
It is well known that superior lateral stability is obtained by a catamaran design or dual hull. Also, included in this art are watercraft which include outrigger floats to increase lateral stability and prevent unintentional tipping. For example, U.S. Pat. No. 5,649,498 to Zigurs and U.S. Pat. No. 5,189,974 to Masters present two dual hull kayaks or kayak catamarans to increase lateral stability and impede overturning. As in a traditional catamaran, these designs involve two parallel boat hulls tied together with an upper flexible platform or braces. Such designs are fairly large and are meant to be operated by two or more persons. They are large and heavy and may require a lifting apparatus or dismantling prior to transport.
U.S. Pat. No. 3,150,386 to Bastien provides a kayak watercraft with removable outriggers and floats to improve lateral stability. This type of design does nothing however, to enable the user to paddle in a straight line but merely provides some resistance to overturning at the cost of increased drag when the outriggers contact the water surface. This type of kayak is clearly unsuitable for white water, however, may be suitable for recreational use on relatively calm waters. The increased weight due to the outriggers and complicated assembly severely restrict commercial viability.
Examples of dual hull multi-person catamarans are common. Examples are provided in U.S. Pat. No. 2,918,031 to Gunderson which provides a common motor boat with a catamaran style hull. U.S. Pat. No. 2,666,406 to Babcock describes a dual hull catamaran speed boat with a conventional two hull base spanned by a platform bridge to support the passengers. Between the dual hull is a tunnel which in the case of a speed boat, has the advantage of compressing air and lifting the speed boat to plane on the water surface. Of course, all catamarans due to the buoyant mass on the laterally outward areas of the hull, substantially increase lateral stability against tipping. Motor boats and sail boats which include a catamaran hull also have superior straight line directional stability compared to traditional hulls, however, at the cost of decreased maneuverability.
It is an object of the present invention to combine the advantageous of a catamaran hull with a single molded plastic or fiberglass personal watercraft application.
It is a particular object of the invention to enhance the enjoyment of traditional kayak and canoe personal watercraft with improved directional and lateral tipping stability of a catamaran design.
It is a further object of the invention to utilize the conventional methods known and understood widely in respect of hollow molded plastic boats to produce a unique double hull kayak in a cost effective and efficient manner.
It is a further object of the invention to produce a hull with reduced wetted surface and resulting drag.